Various home network standards have now become available for networking of appliances in the domestic area. In particular, the IEEE 1394 bus standard has become established in the field of entertainment electronics. This allows communication between the entertainment electronic appliances at a very high data rate. Data rates of 100, 200 and 400 Mbit/s are supported. This is sufficient to transmit asynchronous data packets for controlling the network stations, as well as isochronous audio and video data streams, in parallel. IEEE Standard 1394, however, specifies only the lower layers of the ISO/OSI reference model for data communication, that is to say the bit transmission layer (physical layer), the data protection layer (Data Link Layer) and parts of the switching layer (Network Layer). The higher layers, that is to say the transport layer, the communication control layer (Session Layer), the presentation layer and the application layer, are, however, unspecified.
A consortium of entertainment electronics companies have also taken on the task of defining the higher layers for interchanging data between entertainment electronic appliances. This standard is known by the abbreviation HAVi, where HAVi stands for Home Audio/Video interoperability. This standard specifies a so-called Interoperability Middleware, which ensures that products from different manufacturers understand one another, that is to say cooperate in order to carry out tasks together via the network.
Another consortium of companies, in particular the computer industry companies led by Microsoft, have started a different initiative for specification of network control software based on the existing Internet Protocol (IP). This network system has become known by the abbreviation UPnP (Universal Plug and Play). In this system, the specification does not relate primarily to entertainment electronic appliances, but other appliances can also be integrated in the network, in particular such as personal computers, domestic appliances in the white good range, such as refrigerators, microwave cookers, washing machines, heating controllers, light controllers, alarm system controllers, etc.
Even though the two home network standards HAVi and UPnP are sometimes regarded as competitors, at least in part they serve a different purpose and a scenario is presupposed in which the two networks can exist alongside one another in a domestic environment, and are connected to one another via a gateway. It should then be possible to control the appliances in the UPnP network from the HAVi network side, and vice versa. The connection unit between the two networks is referred to in the following text as a gateway. The expression gateway is frequently not the same as the other expression bridge circuit or bridge, which is likewise used. In some cases, however, the difference between a bridge circuit and a gateway is that a bridge circuit transmits the data packets on the data protection layer to the respective other network while, in contrast, in the case of a gateway, the data packets are in fact transmitted at a higher level in the ISO/OSI reference model.
The work so far relating to gateways for the connection of HAVi and UPnP networks has always been based on a so-called “proxy-based gateway” approach. This conceals the following: in order that the UPnP network stations are visible from an HAVi appliance, the UPnP appliances are represented on the HAVi side in the gateway by so-called HAVi-DCMs. DCM in this case stands for Device Control Module. These additional DCMs are then logged in the HAVi network and can be addressed from the HAVi appliances. One DCM is in this case required for each UPnP network station. If the network station offers different functionalities, such as a television which has the function of a tuner, of an amplifier and of a display unit, then a number of so-called FCMs may be provided for each DCM. An FCM is in this case a so-called functional component module, by means of which an appliance functionality is thus covered.
Conversely, the HAVi network stations should also be addressed from the UPnP side. On the UPnP side, an HAVi appliance is represented by a so-called UPnP device. This means that a corresponding UPnP device is also provided in the gateway for each HAVi network station. A so-called XML appliance description exists for each UPnP device. In this case, XML stands for the description language Extension Markup Language. The corresponding feature for an HAVi FCM on the UPnP side is a so-called service. A number of UPnP services can thus be described in one UPnP device. The conversion between HAVi DCM/FCM and UPnP devices/services should be as complete as possible. However, if the two standards are compared, it is evident that such complete conversion is not always possible.
UPnP appliances invariably originate from areas beyond entertainment electronic appliances, so that the functionalities of such appliances, such as a washing machine, cannot easily be mapped onto the normal functionalities of entertainment electronic appliances. How this can nevertheless still be successfully accomplished for the representation of UPnP appliances on the HAVi side is evident from the previous European Patent Application EP 02 090 147.6 from the same applicant.